1. Field of the Invention
The present invention is directed to a method of inhibiting superoxide generation using phenolic thioether acids which inhibit the generation of superoxide.
2. Background Information and Related Art
Recently, oxygen radicals have been implicated in the pathogenesis of many diseases. This implication is reflected by the many conferences devoted to this topic, books on the subject of free radicals and disease, and the appearance of two new specialized journals: Free Radical Research Communications, and Free Radical Biology and Medicine.
Much is known about the physicochemical properties of the various oxygen radicals, but knowledge of their overall importance in the initiation and amplification of human disease is limited. Some clinical conditions in which oxygen radicals are thought to be involved are discussed in Cross, C. E., et al., "Oxygen Radicals and Human Disease," ANN. INT. MED., 107:526-545 (1987) (see Table 1, p. 527) and Ward, P. A., et al., "Oxygen Radicals, Inflammation, and Tissue Injury," FREE RADICAL BIOLOGY & MEDICINE, 5:403-408 (1988). Among the clinical conditions in which oxygen radicals are thought to be involved are, for example, inflammatory-immune injury, autoimmune diseases, ischemia-reflow states, aging disorders, cancer, cigarette-smoke effects, emphysema, acute respiratory distress syndrome (ARDS), atherosclerosis, rheumatoid arthritis, senile dementia, cataractogenesis, retinopathy of prematurity, radiation injury and contact dermatitis.
Oxygen radicals are capable of reversibly or irreversibly damaging compounds of all biochemical classes, including nucleic acids, protein and free amino acids, lipids and lipoproteins, carbohydrates, and connective tissue macromolecules. These species may have an impact on such cell activities as membrane function, metabolism, and gene expression. Oxygen radicals are formed in tissues by many processes (see Cross, et al., p. 528, Table 2). These are believed to be both endogenous, such as mitochondrial, microsomal and chloroplast electron transport chains; oxidant enzymes such as xanthine oxidase, indoleamine dioxygenase, tryptophan dioxygenase, galactose oxidase, cyclooxygenase, lipoxygenase, and monoamine oxidase; phagocytic cells such as neutrophils, monocytes and macrophages, eosinophils, and endothelial cells; and antioxidation reactions; and exogenous, such as redoxcycling substances, drug oxidations, cigarette smoke, ionizing radiation, sunlight, heat shock and substances that oxidize glutathione. They may be involved in the action of toxins such as paraquat, cigarette smoke, and quinone antitumor drugs.
Various thioether compounds have been described previously. For example, U.S. Pat. No. 4,711,903 and its continuation-in-part, U.S. Pat. No. 4,755,524 disclose compounds of the formula ##STR2## wherein: R.sub.1 and R.sub.2 are the same or different and independently represent tert-alkyl or phenyl; A represents methylene or methylene substituted by alkyl, dialkyl or hydroxy, provided that when A includes hydroxymethylene, the hydroxymethylene group is not adjacent to a heteroatom; B represents sulfur, sulfoxide, sulfone, oxygen, --NH-- or nitrogen substituted by alkyl, phenyl, benzyl, substituted phenyl or substituted benzyl; C represents methylene or methylene substituted by alkyl; R.sub.3 represents CO.sub.2 H, CO.sub.2 -alkyl or a tetrazole group; m is 0 or 1, n is 2, 3 or 4 and p is 1, 2 or 3; and the pharmaceutically acceptable salts thereof. The compounds are specific inhibitors of 5-lipoxygenase and are useful in the treatment of local and systematic inflammation, allergy and hypersensitivity reactions and other disorders in which agents formed in the 5-lipoxygenase metabolic pathway are involved. There is no disclosure of superoxide inhibiting activity.
European Patent Application publication No. 0131221 discloses compounds of the formula ##STR3## in which Ar is phenyl or phenyl substituted by one to three of varied substituents, for example, alkyl, alkoxy, hydroxy, etc.; Q is oxygen, sulfur or an NH group; A is straight or branched chain, optionally substituted, alkylene and R is hydrogen or straight or branched alkyl, optionally substituted by alkoxy, hydroxyl, carboxyl, alkoxycarbonyl, etc.; and n is 0, 1 or 2. The disclosed compounds are indicated to have anti-inflammatory and anti-allergic properties through inhibition of undefined anaphylactic and anaphylactoid reactions, although no test data are provided. The preferred compounds are stated to be those in which Q represents oxygen and n is 0 without mention of any preference among the numerous possible substituents for R or substituted phenyl as Ar. In contrast to the invention disclosed in EPA 0131221, the compounds used in the method of the present invention all have a sulfur atom at the position corresponding to Q as well as having di(tertiary)-alkyl or diphenyl groups as substituents on the phenol moiety corresponding to the substituted Ar group in the above publication which, as described therein, may or may not comprise a phenol. The compounds of Formula I of the present invention, including their surprising specific superoxide inhibitory properties, are, therefore, not specifically described in EPA 0131221.